blob: cf2298d7eeb7c21e4770c4a6508d555fdb7c874c [file] [log] [blame]
"""multipart/form-data encoding module
This module provides functions that faciliate encoding name/value pairs
as multipart/form-data suitable for a HTTP POST or PUT request.
multipart/form-data is the standard way to upload files over HTTP"""
__all__ = ['gen_boundary', 'encode_and_quote', 'MultipartParam',
'encode_string', 'encode_file_header', 'get_body_size', 'get_headers',
import uuid
def gen_boundary():
"""Returns a random string to use as the boundary for a message"""
return uuid.uuid4().hex
except ImportError:
import random, sha
def gen_boundary():
"""Returns a random string to use as the boundary for a message"""
bits = random.getrandbits(160)
import urllib, re, os, mimetypes
from email.header import Header
except ImportError:
# Python 2.4
from email.Header import Header
def encode_and_quote(data):
"""If ``data`` is unicode, return urllib.quote_plus(data.encode("utf-8"))
otherwise return urllib.quote_plus(data)"""
if data is None:
return None
if isinstance(data, unicode):
data = data.encode("utf-8")
return urllib.quote_plus(data)
def _strify(s):
"""If s is a unicode string, encode it to UTF-8 and return the results,
otherwise return str(s), or None if s is None"""
if s is None:
return None
if isinstance(s, unicode):
return s.encode("utf-8")
return str(s)
class MultipartParam(object):
"""Represents a single parameter in a multipart/form-data request
``name`` is the name of this parameter.
If ``value`` is set, it must be a string or unicode object to use as the
data for this parameter.
If ``filename`` is set, it is what to say that this parameter's filename
is. Note that this does not have to be the actual filename any local file.
If ``filetype`` is set, it is used as the Content-Type for this parameter.
If unset it defaults to "text/plain; charset=utf8"
If ``filesize`` is set, it specifies the length of the file ``fileobj``
If ``fileobj`` is set, it must be a file-like object that supports
Both ``value`` and ``fileobj`` must not be set, doing so will
raise a ValueError assertion.
If ``fileobj`` is set, and ``filesize`` is not specified, then
the file's size will be determined first by stat'ing ``fileobj``'s
file descriptor, and if that fails, by seeking to the end of the file,
recording the current position as the size, and then by seeking back to the
beginning of the file.
``cb`` is a callable which will be called from iter_encode with (self,
current, total), representing the current parameter, current amount
transferred, and the total size.
def __init__(self, name, value=None, filename=None, filetype=None,
filesize=None, fileobj=None, cb=None): = Header(name).encode()
self.value = _strify(value)
if filename is None:
self.filename = None
if isinstance(filename, unicode):
# Encode with XML entities
self.filename = filename.encode("ascii", "xmlcharrefreplace")
self.filename = str(filename)
self.filename = self.filename.encode("string_escape").\
replace('"', '\\"')
self.filetype = _strify(filetype)
self.filesize = filesize
self.fileobj = fileobj
self.cb = cb
if self.value is not None and self.fileobj is not None:
raise ValueError("Only one of value or fileobj may be specified")
if fileobj is not None and filesize is None:
# Try and determine the file size
self.filesize = os.fstat(fileobj.fileno()).st_size
except (OSError, AttributeError):
try:, 2)
self.filesize = fileobj.tell()
raise ValueError("Could not determine filesize")
def __cmp__(self, other):
attrs = ['name', 'value', 'filename', 'filetype', 'filesize', 'fileobj']
myattrs = [getattr(self, a) for a in attrs]
oattrs = [getattr(other, a) for a in attrs]
return cmp(myattrs, oattrs)
def reset(self):
if self.fileobj is not None:
elif self.value is None:
raise ValueError("Don't know how to reset this parameter")
def from_file(cls, paramname, filename):
"""Returns a new MultipartParam object constructed from the local
file at ``filename``.
``filesize`` is determined by os.path.getsize(``filename``)
``filetype`` is determined by mimetypes.guess_type(``filename``)[0]
``filename`` is set to os.path.basename(``filename``)
return cls(paramname, filename=os.path.basename(filename),
fileobj=open(filename, "rb"))
def from_params(cls, params):
"""Returns a list of MultipartParam objects from a sequence of
name, value pairs, MultipartParam instances,
or from a mapping of names to values
The values may be strings or file objects, or MultipartParam objects.
MultipartParam object names must match the given names in the
name,value pairs or mapping, if applicable."""
if hasattr(params, 'items'):
params = params.items()
retval = []
for item in params:
if isinstance(item, cls):
name, value = item
if isinstance(value, cls):
assert == name
if hasattr(value, 'read'):
# Looks like a file object
filename = getattr(value, 'name', None)
if filename is not None:
filetype = mimetypes.guess_type(filename)[0]
filetype = None
retval.append(cls(name=name, filename=filename,
filetype=filetype, fileobj=value))
retval.append(cls(name, value))
return retval
def encode_hdr(self, boundary):
"""Returns the header of the encoding of this parameter"""
boundary = encode_and_quote(boundary)
headers = ["--%s" % boundary]
if self.filename:
disposition = 'form-data; name="%s"; filename="%s"' % (,
disposition = 'form-data; name="%s"' %
headers.append("Content-Disposition: %s" % disposition)
if self.filetype:
filetype = self.filetype
filetype = "text/plain; charset=utf-8"
headers.append("Content-Type: %s" % filetype)
return "\r\n".join(headers)
def encode(self, boundary):
"""Returns the string encoding of this parameter"""
if self.value is None:
value =
value = self.value
if"^--%s$" % re.escape(boundary), value, re.M):
raise ValueError("boundary found in encoded string")
return "%s%s\r\n" % (self.encode_hdr(boundary), value)
def iter_encode(self, boundary, blocksize=4096):
"""Yields the encoding of this parameter
If self.fileobj is set, then blocks of ``blocksize`` bytes are read and
total = self.get_size(boundary)
current = 0
if self.value is not None:
block = self.encode(boundary)
current += len(block)
yield block
if self.cb:
self.cb(self, current, total)
block = self.encode_hdr(boundary)
current += len(block)
yield block
if self.cb:
self.cb(self, current, total)
last_block = ""
encoded_boundary = "--%s" % encode_and_quote(boundary)
boundary_exp = re.compile("^%s$" % re.escape(encoded_boundary),
while True:
block =
if not block:
current += 2
yield "\r\n"
if self.cb:
self.cb(self, current, total)
last_block += block
raise ValueError("boundary found in file data")
last_block = last_block[-len(encoded_boundary)-2:]
current += len(block)
yield block
if self.cb:
self.cb(self, current, total)
def get_size(self, boundary):
"""Returns the size in bytes that this param will be when encoded
with the given boundary."""
if self.filesize is not None:
valuesize = self.filesize
valuesize = len(self.value)
return len(self.encode_hdr(boundary)) + 2 + valuesize
def encode_string(boundary, name, value):
"""Returns ``name`` and ``value`` encoded as a multipart/form-data
variable. ``boundary`` is the boundary string used throughout
a single request to separate variables."""
return MultipartParam(name, value).encode(boundary)
def encode_file_header(boundary, paramname, filesize, filename=None,
"""Returns the leading data for a multipart/form-data field that contains
file data.
``boundary`` is the boundary string used throughout a single request to
separate variables.
``paramname`` is the name of the variable in this request.
``filesize`` is the size of the file data.
``filename`` if specified is the filename to give to this field. This
field is only useful to the server for determining the original filename.
``filetype`` if specified is the MIME type of this file.
The actual file data should be sent after this header has been sent.
return MultipartParam(paramname, filesize=filesize, filename=filename,
def get_body_size(params, boundary):
"""Returns the number of bytes that the multipart/form-data encoding
of ``params`` will be."""
size = sum(p.get_size(boundary) for p in MultipartParam.from_params(params))
return size + len(boundary) + 6
def get_headers(params, boundary):
"""Returns a dictionary with Content-Type and Content-Length headers
for the multipart/form-data encoding of ``params``."""
headers = {}
boundary = urllib.quote_plus(boundary)
headers['Content-Type'] = "multipart/form-data; boundary=%s" % boundary
headers['Content-Length'] = str(get_body_size(params, boundary))
return headers
class multipart_yielder:
def __init__(self, params, boundary, cb):
self.params = params
self.boundary = boundary
self.cb = cb
self.i = 0
self.p = None
self.param_iter = None
self.current = 0 = get_body_size(params, boundary)
def __iter__(self):
return self
def next(self):
"""generator function to yield multipart/form-data representation
of parameters"""
if self.param_iter is not None:
block =
self.current += len(block)
if self.cb:
self.cb(self.p, self.current,
return block
except StopIteration:
self.p = None
self.param_iter = None
if self.i is None:
raise StopIteration
elif self.i >= len(self.params):
self.param_iter = None
self.p = None
self.i = None
block = "--%s--\r\n" % self.boundary
self.current += len(block)
if self.cb:
self.cb(self.p, self.current,
return block
self.p = self.params[self.i]
self.param_iter = self.p.iter_encode(self.boundary)
self.i += 1
def reset(self):
self.i = 0
self.current = 0
for param in self.params:
def multipart_encode(params, boundary=None, cb=None):
"""Encode ``params`` as multipart/form-data.
``params`` should be a sequence of (name, value) pairs or MultipartParam
objects, or a mapping of names to values.
Values are either strings parameter values, or file-like objects to use as
the parameter value. The file-like objects must support .read() and either
.fileno() or both .seek() and .tell().
If ``boundary`` is set, then it as used as the MIME boundary. Otherwise
a randomly generated boundary will be used. In either case, if the
boundary string appears in the parameter values a ValueError will be
If ``cb`` is set, it should be a callback which will get called as blocks
of data are encoded. It will be called with (param, current, total),
indicating the current parameter being encoded, the current amount encoded,
and the total amount to encode.
Returns a tuple of `datagen`, `headers`, where `datagen` is a
generator that will yield blocks of data that make up the encoded
parameters, and `headers` is a dictionary with the assoicated
Content-Type and Content-Length headers.
>>> datagen, headers = multipart_encode( [("key", "value1"), ("key", "value2")] )
>>> s = "".join(datagen)
>>> assert "value2" in s and "value1" in s
>>> p = MultipartParam("key", "value2")
>>> datagen, headers = multipart_encode( [("key", "value1"), p] )
>>> s = "".join(datagen)
>>> assert "value2" in s and "value1" in s
>>> datagen, headers = multipart_encode( {"key": "value1"} )
>>> s = "".join(datagen)
>>> assert "value2" not in s and "value1" in s
if boundary is None:
boundary = gen_boundary()
boundary = urllib.quote_plus(boundary)
headers = get_headers(params, boundary)
params = MultipartParam.from_params(params)
return multipart_yielder(params, boundary, cb), headers